Abstract
In this work, the effect of Si doping on InAs/GaAs quantum dot solar cells with AlAs cap layers is studied. The AlAs cap layers suppress the formation of the wetting layer during quantum dot growth. This helps achieve quantum dot state filling, which is one of the requirements for strong sub-bandgap photon absorption in the quantum dot intermediate band solar cell, at lower Si doping density. Furthermore, the passivation of defect states in the quantum dots with moderate Si doping is demonstrated, which leads to an enhancement of the carrier lifetime in the quantum dots, and hence the open-circuit voltage.
Highlights
Since the concept of the intermediate band solar cell (IBSC) was proposed in 1997, significant efforts have been made to realise IBSCs with efficiencies that exceed the Shockley-Queisser limit of 31 % [1]
One of the candidates for the high-efficiency IBSC is the quantum dot intermediate band solar cell (QD-IBSC), which utilises the discrete nature of the carrier density of states and the bandgap tunability of quantum dots (QDs)
Thermal decoupling needs to be achieved between the IB and the conduction band (CB) of wetting layer (WL)
Summary
Since the concept of the intermediate band solar cell (IBSC) was proposed in 1997, significant efforts have been made to realise IBSCs with efficiencies that exceed the Shockley-Queisser limit of 31 % [1]. One of the candidates for the high-efficiency IBSC is the quantum dot intermediate band solar cell (QD-IBSC), which utilises the discrete nature of the carrier density of states and the bandgap tunability of quantum dots (QDs). We report the saturation of strain-induced dislocations and QD state filling by Si-doping QDs in InAs/GaAs QDSCs with AlAs CLs. Previously, we demonstrated that the deposition of AlAs CLs on InAs QDs could suppress the formation of the WL [8]. QD state filling, which is essential for strong two-photon absorption, is observed with significantly lower Si doping densities when compared with that of our previous study [9]
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